1
00:00:00,000 --> 00:00:04,000

2
00:00:04,004 --> 00:00:08,004

3
00:00:08,007 --> 00:00:12,007

4
00:00:12,008 --> 00:00:16,008

5
00:00:16,010 --> 00:00:20,010

6
00:00:20,011 --> 00:00:24,011

7
00:00:24,012 --> 00:00:28,012

8
00:00:28,014 --> 00:00:32,014
เนื้อหาของวันนี้นะคะ ครั้งที่แล้วครั้งที่ 23

9
00:00:32,014 --> 00:00:36,014

10
00:00:36,016 --> 00:00:40,016

11
00:00:40,017 --> 00:00:44,017

12
00:00:44,019 --> 00:00:48,019
ข้อที่ 1 นะคะ ข้อ 1 เป็นลำดับเลขาค

13
00:00:48,020 --> 00:00:52,020

14
00:00:52,021 --> 00:00:56,021

15
00:00:56,022 --> 00:01:00,022

16
00:01:00,022 --> 00:01:04,022
เมื่อเป็นลำดับเลขาคณิตแล้ว

17
00:01:04,023 --> 00:01:08,023

18
00:01:08,024 --> 00:01:12,024

19
00:01:12,025 --> 00:01:16,025

20
00:01:16,027 --> 00:01:20,027
ข้อ 4 เป็นลำดับเลขคณิตที่มีส่วนร่วม

21
00:01:20,029 --> 00:01:24,029

22
00:01:24,030 --> 00:01:28,030

23
00:01:28,031 --> 00:01:32,031

24
00:01:32,032 --> 00:01:36,032
ลำดับเลขาคณิตจะ

25
00:01:36,037 --> 00:01:40,037

26
00:01:40,038 --> 00:01:44,038

27
00:01:44,040 --> 00:01:48,040

28
00:01:48,041 --> 00:01:52,041
และนักเรียนจะได้ทราบพจน์ทั่วไปของเลขาคณิต

29
00:01:52,043 --> 00:01:56,043

30
00:01:56,043 --> 00:02:00,043

31
00:02:00,044 --> 00:02:04,044

32
00:02:04,045 --> 00:02:08,045
+1 หารด้วย พจน์ an จะได้

33
00:02:08,046 --> 00:02:12,046

34
00:02:12,048 --> 00:02:16,048

35
00:02:16,049 --> 00:02:20,049

36
00:02:20,049 --> 00:02:24,049
an = a1 คูณด้วย r ยกกำลัง -1

37
00:02:24,052 --> 00:02:28,052

38
00:02:28,052 --> 00:02:32,052

39
00:02:32,054 --> 00:02:36,054

40
00:02:36,056 --> 00:02:40,056
เริ่มกันที่ข้อแรกกันดีกว่า เริ่มที่ข้อ 1 ค่ะ

41
00:02:40,057 --> 00:02:44,057

42
00:02:44,058 --> 00:02:48,058

43
00:02:48,059 --> 00:02:52,059

44
00:02:52,061 --> 00:02:56,061
อะไรมาข้อนี้โจมตีกำหนด a1 ให้

45
00:02:56,062 --> 00:03:00,062

46
00:03:00,063 --> 00:03:04,063

47
00:03:04,064 --> 00:03:08,064

48
00:03:08,066 --> 00:03:12,066
หารด้วย -2

49
00:03:12,070 --> 00:03:16,070

50
00:03:16,072 --> 00:03:20,072

51
00:03:20,074 --> 00:03:24,074

52
00:03:24,074 --> 00:03:28,074
พอเราได้สูตรทั่วไปแล้ว

53
00:03:28,076 --> 00:03:32,076

54
00:03:32,077 --> 00:03:36,077

55
00:03:36,078 --> 00:03:40,078

56
00:03:40,080 --> 00:03:44,080
ข้อนี้ได้ a10 เป็น 4,096

57
00:03:44,084 --> 00:03:48,084

58
00:03:48,085 --> 00:03:52,085

59
00:03:52,086 --> 00:03:56,086

60
00:03:56,087 --> 00:04:00,087
ของลำดับเลขาคณิต

61
00:04:00,088 --> 00:04:04,088

62
00:04:04,089 --> 00:04:08,089

63
00:04:08,090 --> 00:04:12,090

64
00:04:12,091 --> 00:04:16,091
หาค่า r นะคะ ก่อนที่เราจะไปทำ

65
00:04:16,091 --> 00:04:20,091

66
00:04:20,092 --> 00:04:24,092

67
00:04:24,094 --> 00:04:28,094

68
00:04:28,096 --> 00:04:32,096
เขียนสูตรพจน์ทั่วไป

69
00:04:32,101 --> 00:04:36,101

70
00:04:36,101 --> 00:04:40,101

71
00:04:40,103 --> 00:04:44,103

72
00:04:44,104 --> 00:04:48,104
จะทำเราจะต้องหาค่า a1 ก่อน

73
00:04:48,106 --> 00:04:52,106

74
00:04:52,107 --> 00:04:56,107

75
00:04:56,108 --> 00:05:00,108

76
00:05:00,110 --> 00:05:04,110
ค่าเศษ 16ส่วน3 ค่ะ

77
00:05:04,112 --> 00:05:08,112

78
00:05:08,114 --> 00:05:12,114

79
00:05:12,115 --> 00:05:16,115
ได้แล้ว ติดสมการนี้ไว้ก่อนเป็นสมการที่ 1

80
00:05:16,116 --> 00:05:20,116

81
00:05:20,117 --> 00:05:24,117

82
00:05:24,118 --> 00:05:28,118
ทำเหมือนเดิมเลยค่ะ นักเรียนแทนค่า

83
00:05:28,120 --> 00:05:32,120

84
00:05:32,121 --> 00:05:36,121

85
00:05:36,122 --> 00:05:40,122
เหมือนกันค่ะ ทำอะไรไม่ได้ ให้เป็นสมการที่ 2

86
00:05:40,123 --> 00:05:44,123

87
00:05:44,124 --> 00:05:48,124

88
00:05:48,124 --> 00:05:52,124
a1 และ r ครูจะนำสมการ

89
00:05:52,125 --> 00:05:56,125

90
00:05:56,126 --> 00:06:00,126

91
00:06:00,127 --> 00:06:04,127
หารด้วยเศษ 16ส่วน3

92
00:06:04,128 --> 00:06:08,128

93
00:06:08,129 --> 00:06:12,129
เราต้องใช้ความรู้เรื่องการหาเศา

94
00:06:12,131 --> 00:06:16,131

95
00:06:16,132 --> 00:06:20,132
ฝั่งขวาของเรา a

96
00:06:20,133 --> 00:06:24,133

97
00:06:24,135 --> 00:06:28,135
ส่วนทางด้านซ้ายนะคะ

98
00:06:28,136 --> 00:06:32,136

99
00:06:32,137 --> 00:06:36,137
เราจะเห็นว่า 81 สามารถเขียน

100
00:06:36,140 --> 00:06:40,140

101
00:06:40,141 --> 00:06:44,141
ได้อีก 1 รูปแบบ 2 ยกกำลัง 4

102
00:06:44,143 --> 00:06:48,143

103
00:06:48,144 --> 00:06:52,144
จะกลายเป็น 3 ยกกำลัง 5

104
00:06:52,144 --> 00:06:56,144

105
00:06:56,145 --> 00:07:00,145

106
00:07:00,147 --> 00:07:04,147

107
00:07:04,150 --> 00:07:08,150

108
00:07:08,152 --> 00:07:12,152

109
00:07:12,153 --> 00:07:16,153

110
00:07:16,153 --> 00:07:20,153

111
00:07:20,155 --> 00:07:24,155

112
00:07:24,156 --> 00:07:28,156

113
00:07:28,158 --> 00:07:32,158

114
00:07:32,160 --> 00:07:36,160

115
00:07:36,160 --> 00:07:40,160

116
00:07:40,161 --> 00:07:44,161

117
00:07:44,163 --> 00:07:48,163

118
00:07:48,164 --> 00:07:52,164

119
00:07:52,166 --> 00:07:56,166

120
00:07:56,168 --> 00:08:00,168

121
00:08:00,169 --> 00:08:04,169

122
00:08:04,170 --> 00:08:08,170

123
00:08:08,172 --> 00:08:12,172

124
00:08:12,174 --> 00:08:16,174

125
00:08:16,176 --> 00:08:20,176

126
00:08:20,179 --> 00:08:24,179

127
00:08:24,181 --> 00:08:28,181

128
00:08:28,182 --> 00:08:32,182

129
00:08:32,183 --> 00:08:36,183

130
00:08:36,188 --> 00:08:40,188

131
00:08:40,189 --> 00:08:44,189

132
00:08:44,192 --> 00:08:48,192

133
00:08:48,194 --> 00:08:52,194

134
00:08:52,195 --> 00:08:56,195

135
00:08:56,196 --> 00:09:00,196

136
00:09:00,197 --> 00:09:04,197

137
00:09:04,199 --> 00:09:08,199

138
00:09:08,200 --> 00:09:12,200

139
00:09:12,201 --> 00:09:16,201

140
00:09:16,202 --> 00:09:20,202

141
00:09:20,205 --> 00:09:24,205

142
00:09:24,206 --> 00:09:28,206

143
00:09:28,208 --> 00:09:32,208

144
00:09:32,210 --> 00:09:36,210

145
00:09:36,212 --> 00:09:40,212

146
00:09:40,214 --> 00:09:44,214

147
00:09:44,215 --> 00:09:48,215

148
00:09:48,217 --> 00:09:52,217

149
00:09:52,219 --> 00:09:56,219

150
00:09:56,222 --> 00:10:00,222

151
00:10:00,224 --> 00:10:04,224

152
00:10:04,226 --> 00:10:08,226

153
00:10:08,228 --> 00:10:12,228

154
00:10:12,230 --> 00:10:16,230

155
00:10:16,231 --> 00:10:20,231

156
00:10:20,232 --> 00:10:24,232

157
00:10:24,234 --> 00:10:28,234

158
00:10:32,236 --> 00:10:35,236

159
00:10:36,238 --> 00:10:39,239

160
00:10:40,239 --> 00:10:43,243

161
00:10:48,242 --> 00:10:51,244

162
00:10:52,243 --> 00:10:55,246

163
00:10:56,244 --> 00:10:59,244

164
00:11:00,246 --> 00:11:00,248

165
00:11:04,250 --> 00:11:04,253

166
00:11:12,256 --> 00:11:12,257

167
00:11:08,254 --> 00:11:08,256